.Unbelievable but we might actually get a clear moonless night here in the south of England tonight. The last time I was able to fire up my astrophotography kit for some deep sky work was May 30th, some 7½ weeks ago!

If we're not jinxing it right now, I just fired up three astro forecasts. Two say clear skies for the next 3 days, one indicting cloud on Tuesday... one regular forecasts says some cloud Monday but clear otherwise 1st half of the week. Outside right now... mostly clear.

I wonder if it's dark enough for me to have another go at narrowband cygnus? That reminds me, I'm going to break the weather again as I've some mounting accessories on my shopping list...

Best of luck. I think (hope) I've finally captured the last subs I needed for my North America nebula mosaic. That allows me to move on and I've just had a look at my first ever sub (1,000 seconds with a red filter) of M31 where I'll be spending some time over the next few clear nights. It just about fits in the frame (a bit tight but I really don't want to do another mosaic for a while) and, even better, Maxim DL seems to be telling me that at f/7 I'm only saturating the central dozen or so (area, not linear) pixels which means I won't have to add any 200 second subs to recover detail in the core. Initial plan is for 5 x 1,000 seconds in each of R, G and B and then a sequence of 15 x 1,500 second subs in Hα but any of those numbers might have to be increased if I feel I'd like deeper and/or cleaner data. What fun.

Bob.

P.S. Yeah, I know: it's been done to death over the years but, crucially so far as personal satisfaction is concerned, not by me!!!

.Just a sneak preview. Here's the result of some very quick and dirty processing of the 5 x 1,000 second subs of M31 I captured last night using a red filter, uncropped except for a 48 pixel clip along each edge and downsized by a factor of four to fit the forum:

Maybe more depth needed (more subs) and there's certainly a more detail in the image than this morning's processing revealed (too nice a day to spend 'pooting). I also captured a couple of 1,000 second subs with the blue filter before light stopped play last night and a quick inspection showed there's good information there. Maybe by the time I've got full set of 5 x 1,000 second subs in R, G and B and combined them to create a luminance channel I'll have enough depth. Hope so!

I just packed up, getting 8x2m Ha and 18x2m SII to add to yesterday's 18x2m of OIII (not 4m subs as I incorrectly wrote). I got some fresh Ha data as I noticed I didn't have previous data in this field of view before. I only had 35mm and 135mm, whereas this set is ending up at 50mm... going for a quick process before bed. As and when we get more clear nights I can try adding to it then.

Speaking of which, with the forecast for tonight looking less good, I thought I'd see how the 10 x 1,500 second Hα subs at f/7 of M31 I've captured over the last couple of nights stack up. I wasn't expecting too much having only looked at the uncorrected (bias/dark/flat) single image subs as they arrived in Maxim DL but having done a quick and dirty integration in PixInsight, with full calibration, I think I might have enough to work with. Quite noisy but the emission nebulae appear to be showing up although I won't really understand what I've caught until I can reprocess all the subs (R,G,B and Hα) together and do a detailed comparison before combining in a way which will make the best eye candy! Here's the result of just over four hours of Hα photon capturing, as before downsized by a factor of four:

That said, a blink comparison, made a bit more difficult by the fact that the two preview images aren't aligned, with my "Red Preview" above shows that the Hα seems to be nicely following the gas and dust lanes rather than just mirroring the brighter red bits. Can't wait to see how this all integrates with the green and blue subs.

I also can't wait to see what it looks like all in. I did give myself a little preview kinda, but aligning and assigning the red and Ha output earlier to separate colour channels. Definitely interesting!

I took a couple of hours out from enjoying the garden and registered and combined various sets of subs. The Hα result looks much like it does in the image above so I tried an idea I had last night. The problem is how to extract the emission nebulae from the bright background continuum contributed by millions of close by stars. It occurred to me that the spectral types of all those stars average out and that the green channel, with minimal contribution from Hβ and none at all from Hα might be useful. Cutting to the chase I used PixInsight's "PixelMath" functionality for the first time to produce a new image by subtracting the green image, reduced in intensity by a factor determined by trial and error of 15, from the Hα image. Here's the result, reduced in scale by a factor of four as usual:

This is yet another quick and dirty tidy up in PhotoShop of the output and I can be less aggressive with the black clipping later on. There are still many stars, local to our own glalxy, to remove but they are easily spotted. What really pleases me is that the Hα emission nebulosity in M31 is now highlighting really well and, as an unexpected bonus, I'm also seeing hints of a spiral structure in what's left of the central bulge of M31. This is awesomely great entertainment and I find myself almost wishing for a rainy day so I can spend the necessary ten or twenty hours really trying to extract the most from the data I have.